Pattern-sensitive epilepsy is a seizure disorder precipitated by visual patterns, particularly stripes. Four patients with pattern-sensitive epilepsy have been studied at the University of Washington and characterized with respect to the stimuli that trigger their EEG epileptiform activity. The spatial frequency, contrast and orientation of striped patterns were found to influence epileptogenicity. These same variables figure prominently in modern psychophysical investigations of pattern perception. A Fourier analysis of the patterns inducing EEG paroxysmal activity in our patients suggests that they are responsive to patterns with rather simple properties in the spatial frequency domain. In particular, the epileptogenic patterns occupy a narrow range of spatial frequencies. The broad objectives of this proposal are to examine two patients for anomalies of pattern vision and to further analyze the epileptogenic stimuli. To these ends, we will determine contrast sensitivity and evoked potentials as functions of pattern contrast and spatial periodicity. Evoked potentials will be examined with regard to form, latency, amplitude and topographic distribution of their component waves. Mechanisms of seizure production will also be studied with split-field and dichoptic techniques. The results of the investigation will be evaluated with respect to the following issues: a. The role, if any, of spatial frequency channels in the disorder. b. The implications for desensitization therapy. c. The mechanisms underlying bilaterally synchronous EEG spike and waves.